PROJECT SUMMARY: Intellectual disability affects 1?3% of the worldwide population; these individuals have deficits in adaptive functioning necessitating ongoing support to perform activities such as dressing, reading, and interpreting the intentions of others. The cost of this support, for a single US patient, is approximately $1?2 million throughout his or her lifespan1. The pathophysiology and etiology of intellectual disability has been difficult to elucidate due to the heterogeneity in casual mutations2. Despite this complexity, mutations linked to intellectual disability tend to accumulate in pathways relating to nervous system development, cellular metabolism, and microtubule based movement and axonal transport3. Additionally, monogenic forms of intellectual disability provide direct insight into defective cell biological processes that underlie intellectual disability. Our lab found that mutations in a ubiquitously expressed zinc-finger, polyadenosine RNA-binding protein, ZC3H14, are linked to a form of monogenic, non-syndromic autosomal recessive intellectual disability4. We developed a Drosophila melanogaster model to investigate the role of dNab2, the fly ortholog to human ZC3H14. Loss of dNab2 results in neuronal, survival, and locomotive phenotypes. Importantly, many of the phenotypes can be rescued by transgenic expression of human ZC3H14 exclusively in neurons, implying a conservation of function from flies to humans and feasibility in using dNab2 to model ZC3H14 function. Data generated from our fly model suggests that dNab2 loss is critical in neurodevelopment, and that it may be regulating gene expression in neurons. However, the identity of mRNA targets of dNab2 in neurons and the mechanism by which it regulates these targets are key gaps in knowledge. Preliminary data suggest that dNab2 interacts functionally with multiple components of the planar cell polarity (PCP) pathway. PCP is a non-canonical branch of Wnt signaling that regulates axon guidance in the nervous system and tissue polarization in somatic tissue 5?8. Therefore, I will directly test the hypothesis that dNab2 regulates PCP components to control neurite extension and guidance during neurodevelopment. The Specific Aims of this project are: 1) define genetic dNab2:PCP interactions in two neurodevelopmental contexts, 2) utilize a systems-level proteomic approach to identify dNab2 regulated pathways in the brain, and 3) examine physical and functional interactions between dNab2 and PCP pathway RNAs in vivo. Aim 1 utilizes Drosophila genetic tools to assess functional genetic interactions with dNab2 in two neuronal cell types. Aim 2 uses network analyses, of a unique Drosophila proteomic dataset, to identify dNab2 regulated pathways. Aim 3 utilizes techniques to assess RNA localization and physical interaction with dNab2. Successful completion of these aims will provide insight into how dNab2 regulates local gene expression to impact neurodevelopment, and thus support our broad, long-term objective of defining the cell biological and molecular mechanisms underlying ZC3H14/dNab2 related neurodevelopmental defects.